Zinc oxide is a semiconductor with a wide band gap of 3.4 eV, which makes it transparent in visible light. Zinc oxide absorbs in the ultraviolet (UV) to blue wavelengths. Zinc oxide naturally has n-type character because of its native defects, such as oxygen vacancies or zinc interstitials. Over the last few years, thin film and bulk ZnO materials have been explored for various applications in electronics, optics and photonics.
The large surface areas of low-dimensional zinc oxide nanostructures, together with their optical and electrical properties, make them desirable for applications such as UV and humidity sensing, field mission and gas sensing. Different methods have been developed to produce one-dimensional zinc oxide nanostructures, including: vapour-liquid-solid growth; thermal evaporation; vapour phase transport; metal organic vapour phase epitaxy; chemical vapour deposition; pulsed laser deposition (PLD); laser ablation; and solution processes. The reported zinc oxide nanostructures include, for example: nanowires; nanorods; nanotubes; nanowalls; nanopropellers; nanocoral reefs; nanonetworks; and quantum wells.
These methods for producing zinc oxide nanostructures typically involve high cost and multiple processing steps. There remains a need for low cost, reproducible, large scale production techniques.
Accordingly, it is an object of the present invention to go some way to avoiding the above disadvantages and/or to at least provide the public with a useful choice.
Other objects of the invention may become apparent from the following description which is given by way of example only.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.